Information codes such as two-dimensional codes are now being used in many applications. A technique in which a photograph, a drawing, or the like is arranged within a code region has also been proposed. For example, a technique provided by patent literature 1 involves a two-dimensional code in which strings of reverse-converted bits that have been reversely converted from strings of bits are determined. These strings of bits form a region in the two-dimensional code that is read as a single gray level. The two-dimensional code is produced by the reverse-converted bit strings being converted based on format information of the two-dimensional code. A unique two-dimensional code that has a design region composed of the single gray level is thereby produced.